Airbrush Colors:
You could simply use colored icing or draw onto the cake if you do not have an airbrush system.Pink for the swirled backgroundNeon Purple for the swirled backgroundYellow for the swirled backgroundNeon Green for the swirled backgroundNeon Blue for the swirled background

Colored Icing:White frosting to ice your entire cake, to outline the clouds and for the dots.Royal Blue for the borders, the writing, the clouds and the dots